Amazon Transcribe Medical - Sample Rate Not Supported

Question

I have a handfull of files with a sample rate of 8000hz and 11025hz.

Amazon's own documentation indicates that the valid MediaSampleRateHertz is between 8000 - 48000 (inclusive, judging by examples).

However running a media transcribe job (both via boto3 and directly on the service in the AWS console) returns failures with reasons:

• The audio sample rate 8000 Hz is not supported. Change the audio sample rate of your media file and try your request again.
• The audio sample rate 11025 Hz is not supported. Change the audio sample rate of your media file and try your request again.

This happens when specifiying the sample rate AND leaving AWS to determine it (which it does correctly).

Where am I going wrong?